Emergency flotation devices are required on many aircraft to provide emergency assistance to passengers in the event the aircraft experiences an emergency situation and is forced down in water. Emergency flotation devices generally include systems designed to float the aircraft, systems for emergency life rafts and life vests for individual occupants.
One example of an airplane flotation system is shown in U.S. Pat. No. 1,776,865. The system includes inflatable bags located in a forward portion of an airplane and is manually operated by a pilot. The bags are stored in a non-inflated state within closed compartments. The system utilizes pressure cylinders to sequentially unlock doors of the compartments and inflate the inflatable bags. During operation the pilot activates the pressure cylinder by releasing pressurized gas. After inflation, the pilot is required to pull a cord that places the pressure cylinder into an intermediate position to block further fluid flow between the pressurized fluid. A first disadvantage of the system is that it does not provide for a valve that remains closed until a predetermined pressure is applied. As a result, any increase in pressure may cause the doors to unlock and the inflatable bags to inflate even when undesired. Another disadvantage is that it requires manual operation by the pilot even after the initial activation of the system.
U.S. Pat. No. 2,264,321 to Manson, describes a life-saving device that includes an inflatable life raft that is arranged in a compartment on the side of a vehicle such as an airplane. The compartment is closed by a pair of hinged doors that are spring-loaded to urge them into an opened position. The doors are held closed by pins that extend through meshing lugs that are included on the doors. A pull cord is secured to the pins and a valve on an inflating-gas container so that pulling on the cord sequentially removes the pins from the lugs and operates the valve to permit the flow of gas from the container to the raft. The cord fully disengages from the gas container after the valve is operated. A first disadvantage of the system is that the pins may be disengaged without a complete activation of the system. In addition, the pull cord may become bound which may result in the pin disengaging without activation of the gas container. A further disadvantage is that there is that the gas container valve does not include a mechanism to close the gas path between the gas container and the raft after the raft is inflated.
In view of the above, there exists a need for a pressure activated latch for an emergency flotation system that provides sequential unlatching and inflation, that will unlatch when subjected to a pressure above a predetermined threshold pressure and that will automatically prevent fluid communication between the pressurized fluid source and the inflatable after inflation.